Discard snapshot manual repairs not working

[otto.behrens]

Hi,

I'm trying to fix up a snapshot discard that went wrong and I still battle to start up my vm. I now get "Could not find a registered hard disk with UUID1".

I've been looking at the VDI Tutorial - very useful, thanks.

I found my chain of parent UUID references, now very similar to the example in the VDI tutorial, by using hexer. I had a redunant .vdi file (UUID1) in my Snapshots directory - this is the one I originally discarded. (my original post). So I moved the file away to tmp.

I edited ~/.VirtualBox/VirtualBox.xml and removed UUID1 from the chain. I bounced all services; still getting something that is looking for UUID1 when I start VBox.

Can you please help me to find what is referencing the snapshot and how I can eliminate it?

Any help will be greatly appreciated - I'm in trouble here (gotta do payroll).

Thanks
Otto

[TerryE]

Otto, when you say you are trying to do a snapshot discard, are you trying to go back to the base VDI or just from N shapshots to N-1?

The first case is the easiest because if you temporarily unregister the VDI and then run VBoxManage internalcommands setvdiuuid, this resets the other pointers as well as the UUID of the VDI itself. You can then reregister the VDI and associate it with the VM.

The N-1 case is more difficult. I am assuming that you have tried to use the VirtualBox GUI and just selected the discard option, but this has failed. If not then try this.

The UUIDs are stored in three locations: the main VirtualBox.xml and Machine.xml registries and the VDI header chains. You need all three to be consistent, and in particular, the last snapshot in the chain must not include and unresolved UUID references. The easiest way to work out which ones must be zero is compare your broken chain with a dummy chain that ha been set up to mirror this configuration. You may need to zero out the relevant entries in the header. Any hex editor can do this, though you may want to back up the VDI header first.

[otto.behrens]

Thanks Terry, this helped me. I missed that the <VM>.xml file contains the snapshot chain. What I understand now is that the VirtualBox.xml file contains the differencing virtual disk information and the <VM>.xml more info on the snapshots.

I fixed up the <VM>.xml file by removing the discarded snapshot and disk uuid. Just booted up the machine, thanks.

[TerryE]

Thanks Otto for letting me know. I am glad you got this working. Hope that the payroll went OK